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posted by Fnord666 on Tuesday September 25 2018, @04:39PM   Printer-friendly
from the chilling-news dept.

MIT researchers have developed a completely passive, solar-powered way of combating ice buildup. The system is remarkably simple, based on a three-layered material that can be applied or even sprayed onto the surfaces to be treated.

It collects solar radiation, converts it to heat, and spreads that heat around so that the melting is not just confined to the areas exposed directly to the sunlight. And, once applied, it requires no further action or power source. It can even do its de-icing work at night, using artificial lighting.

Icing is a major problem for aircraft, for wind turbines, power lines, offshore oil platforms, and many other places. The conventional ways of getting around it are de-icing sprays or by heating, but those have issues.

The team has achieved with the three-layered material they've developed. The top layer is an absorber, which traps incoming sunlight and converts it to heat. The three layers, all made of inexpensive commercially available material, are then bonded together, and can be bonded to the surface that needs to be protected. For some applications, the materials could instead be sprayed onto a surface.

[...] The system could find even wider commercial uses, such as panels to prevent icing on roofs of homes, schools, and other buildings.

http://www.rtoz.org/2018/09/08/a-new-way-to-remove-ice-buildup-without-power-or-chemicals/

Also at http://news.mit.edu/2018/remove-ice-buildup-airplanes-wind-turbines-solar-power-0831


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  • (Score: 1, Informative) by Anonymous Coward on Tuesday September 25 2018, @04:47PM (7 children)

    by Anonymous Coward on Tuesday September 25 2018, @04:47PM (#739746)

    Our dehumidifier ices up if it runs too long (damp basement in the summer). Best solution I've found is to use the cycle timer instead of the humidity sensor, so it's set to run 3 hours, then off for 3 hours. Setting the "humidity" to, say, 50% RH is almost guaranteed to run a too aggressive duty cycle and after a day it's fully iced, and not generating any more water.

    What I'd really like is a way to sense when ice is starting, turn off until melted (or de-ice with something like tfa) and then turn right back on again.

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  • (Score: 1, Informative) by Anonymous Coward on Tuesday September 25 2018, @10:55PM

    by Anonymous Coward on Tuesday September 25 2018, @10:55PM (#739915)

    If it is icing up, you need a new one. There are many issues that can cause that, from the thermocouples failing, to refrigerant leakage, to using the wrong size. Plus, if it is a non-energy star unit where the fan turns off when the compressor is off, that can cause icing and other problems. Around here, we replaced our dehumidifier with an Energy Star unit and saw a huge reduction in both the energy bills and the humidity in the air. We've already paid it off from the savings in the electric bill.

  • (Score: 1) by WolvesOfTheNight on Wednesday September 26 2018, @01:59AM (5 children)

    by WolvesOfTheNight (4704) on Wednesday September 26 2018, @01:59AM (#740004)

    What I'd really like is a way to sense when ice is starting

    You can detect it using by measuring the dielectric constant using an impedance analyzer [researchgate.net]. Of course, you would have to wire up something to measure the impedance, figure out how to tell ice from water & air, and hook it up to your control system. Which reminds me, I need to see about offering an update to the Arduino AD5933 library on gethub...

    • (Score: 1, Insightful) by Anonymous Coward on Wednesday September 26 2018, @03:44AM (4 children)

      by Anonymous Coward on Wednesday September 26 2018, @03:44AM (#740021)

      It is even easier than that. All you need to do is measure the temp of the cool side of the system. The system will start to warm because of the insanely large amount of energy required for the deposition of the water vapor. Once it cools again, the layer of ice has built up enough to insulate the sensor. You then switch to warming mode, and you know you are done when the temp rises above freezing, as the energy required to melt the ice will prevent that. Then you can repeat the cycle once cooling begins.

      • (Score: 1) by WolvesOfTheNight on Wednesday September 26 2018, @04:24AM (3 children)

        by WolvesOfTheNight (4704) on Wednesday September 26 2018, @04:24AM (#740030)

        Yea, under these circumstances, that probably is a better way.

        • (Score: 0) by Anonymous Coward on Wednesday September 26 2018, @01:41PM (2 children)

          by Anonymous Coward on Wednesday September 26 2018, @01:41PM (#740161)

          OP here, thanks for your comments.

          This makes sense, so why isn't this simple control strategy used? Adding a temp sensor can't cost very much and these home units already have a processor in them to read the "humidity sensor", run the display and timer.
          Playing the manufacturer for a moment, I suppose it's another thing to be assembled so it would add cost, and it's also another point of failure (more warranty costs).

          • (Score: 1) by WolvesOfTheNight on Wednesday September 26 2018, @06:30PM (1 child)

            by WolvesOfTheNight (4704) on Wednesday September 26 2018, @06:30PM (#740367)

            My guess is that it sometimes is used. I am not sure how hard it would be to characterize the temperature behavior of the system to correctly trigger deicing. There may be confounding factors, such as extreme outside (or inside) temperatures changing the average system temperature enough to mess with the control system. Also, you may have trouble with partial deicing or over deicing (heating up the contents). But it sounds like a pretty straight forward approach.

            I recall seeing what I thought was a thermometer on the return side of an evaporator when I was fixing my refrigerator. But I am not currently interested enough in the topic to really dig into it at the moment (I read up on the impedance approach to detecting ice while working on something else). A quick search on Google scholar found several approaches being used for triggering a de-icing mechanism on a refrigerator, mostly in patent fillings. At a glance, they involved either a timer or some form of ice detection, but I didn't dig into them. Might be worth a check if you are really interested. Or maybe you can find a text on refrigerator design somewhere...

            • (Score: 0) by Anonymous Coward on Friday September 28 2018, @02:39AM

              by Anonymous Coward on Friday September 28 2018, @02:39AM (#741168)

              Most refrigerators and dehumidifiers use timers or temp sensors, as they are the simplest and accurate enough for those approaches. My guess, based on what OP said, is that his units are probably 5-10 years old and have leaked a large amount of refrigerant. The problem with thermometer feedback systems is that they cannot properly adapt to low refrigerant levels. The reason why is that leaking refrigerant causes the pressure in the evaporator it decrease too much, which means the cool side is too cold. The thermometer, therefore, never triggers the appropriate temperature rise to trigger de-icing without larger amounts of ice present, which leads to a even more problems. Basically, as the pressure levels in the system drop, the dehumidifier gets too cold and ices over causes damage to the coils and the heat sink through both physical and chemical processes. This causes the process to accelerate as the microscopic holes increase in number and size. This causes the pressure to drop, causing lower operating temps. And on and on. It is made worse by the fact that many old dehumidifiers don't run the fan during the warm cycle, slowing melting and skewing temp reads.

              TL;DR replace your dehumidifier with a properly sized new unit and thank me later.